The Atmosphere

Air and Air Pressure

What is Gay-Lussac’s Law and why is it important in meteorology?

Joseph Louis Gay-Lussac (1778–1850) was a French physicist and chemist best known for two laws of physics about gases. One of these laws states that, in chemical reactions, gases combine in simple ratios according to volume. For example, it takes two carbon monoxide molecules (CO) to combine with one oxygen molecule (O2) to create carbon dioxide (CO2). This became known as Gay-Lussac’s Law and is important for understanding chemical reactions of gases within our atmosphere. Gay-Lussac also published a law about gas expansion by volume occurring linearly as a function of temperature. Sometimes credited as another of Gay-Lussac’s laws, it is more correctly called Charles’ Law (and Gay-Lussac was one of those who gave credit where it was due). It was discovered by another French physicist, Jacques Alexandre César Charles (1746–1823), who was also a mathematician. Charles found that gases such as oxygen and nitrogen increased their volume by 1/273 for every 1.8°F (1°C) increase in temperature. From this, he extrapolated the possibility that, at absolute zero (-273°C, or –459.4°F) the volume of a gas would also be zero. Both scientists were also balloonists, which was handy, given their interest in the atmosphere.